The present invention relates to machine tools for alternately punching and thermally cutting a sheet-like workpiece, and especially those devices which are automatically controlled as to much of their operations by a computer control with the workpiece being moved relative to a work station by a workpiece clamping and guidance system.
Various machine tools have been proposed for performing machining, punching, stamping, bending and other functions upon sheet metal workpieces. Of recent years, the usage of computer numerically controlled workpiece guidance systems to move the workpiece relative to a work station on such machines has become highly advantageous. Because of the cost of accurate guidance systems for moving the workpiece and of the computer controls, it has been recognized as desirable to provide multiple functions in a single machine tool so as to utilize these two expensive components in the course of performing different functions upon the workpiece.
It is known that it may be desirable to perform both thermal cutting and punching of a sheet metal workpiece in a single machine in order to achieve this beneficial result. In Brolund et al. U.S. Pat. No. 4,063,059 granted Dec. 13, 1977, there is disclosed a punch press which additionally incorporates a plasma cutting head at a position to one side of the punching head, and the workpiece is moved for working between the punching station and the thermal cutting station. In Clark et al. U.S. Pat. No. Re. 31,042 granted on Sept. 28, 1982, there is disclosed a machine having a punching station and a laser cutting head disposed at a position to one side of the punch head and the workpiece is moved between the punching and thermal cutting stations by the guidance system. Although in theory it would be possible to perform punching and thermal cutting operations simultaneously in these two machines in view of the fact that the work stations are offset, in practice this has not been feasible. Thus, the machine is selectively performing either punching or thermal cutting with the workpiece being shifted between the two workstations depending upon the function to be performed at any given time.
It will be appreciated that this practice requires the shifting of the workpiece from the zero position represented by the punching station to an offset position represented by the thermal cutting station. Clearly, there must be a high degree of accuracy in the guidance system and in the computer control system to insure that apertures are formed in the workpiece precisely as desired. Moreover, time is required to effect the shifting between the two stations and there is generally an increase in the cost of the machine reflected by the need to provide the separate work station for thermal cutting and programming control for a second station. A further problem may be the generation of a potential dead area, i.e., an area of the sheet which may not be available to be worked on by the machine without reorientation of the sheet within the clamping and guidance mechanism.
It is an object of the present invention to provide a novel machine tool which will provide both punching and thermal cutting at precisely the same work station.
It is also an object to provide such a machine in which the tools for punching and thermal cutting may be interchanged at the work station rapidly and effectively.
Another object is to provide such a machine in which the punching and thermal cutting tools may be automatically exchanged at the work station.
A further object is to provide such a machine which is of rugged construction and adapted to precision manufacture so as to insure highly accurate processing of workpieces.